One thing that bothers me(for aesthetic reasons) about the mass fabricator is that it requires a redstone signal to stay -off- rather than one to stay -on- like the other machines(rotary macerator, induction furnace, etc)
this means that I need the use of a redstone inverter to allow a switch on a wall to turn on and off the device in the same orientation as the switches for my other machines(all my other machines use up as off and down as on, however the mass fabricator requires the switch me up when on, and down when off unless I invert the signal)
this requires me to use more space in my wiring area to do the inversion, and therefore reduces the amount of things I can do with my wiring area for other purpose.
so my suggestion is simply to reverse this. make the mass fabricator off by default(unless there is scrap in it) and on with a redstone signal.